The Amiga computer treats a screen as a drawable area that can have its own resolution and colour depth, and a program can open any number of such screens simultaneously, each with different settings. Unlike today’s fixed‑resolution monitors, the Amiga’s original graphics hardware (OCS) allowed programmers to define separate screens for different tasks, for example a low‑resolution text editor and a high‑resolution image viewer, and switch between them instantly. This flexibility came from the system’s treatment of memory as a shared resource, where the amount of video memory allocated to a screen could be varied on the fly.
Colour on an Amiga screen comes from indexed palettes: a limited set of colour registers hold values taken from a 12‑bit colour space (later expanded to 24‑bit on the AGA chipset). The number of available colours is increased by adding bitplanes; each extra plane doubles the palette size, so one bitplane gives two colours, two planes four, and up to five planes on the original hardware provide 32 colours, while AGA extends this to eight planes for 256 colours. Beyond the palette, the copper co‑processor can change a colour register once per horizontal line, producing gradients and effectively raising the on‑screen colour count without extra memory. The Amiga also supports dual playfields, where colour index 0 of the frontmost screen becomes transparent, revealing the screen underneath while all other indices remain intact, and users can drag a screen’s title bar to pull it down and expose another screen behind it.
These capabilities were meaningful because memory was expensive and the Amiga’s stock configuration shared a small amount of RAM between CPU, video and audio hardware, making fine control over video memory essential. Although the mechanical novelty of screen dragging impressed users in the mid‑1980s, modern multitasking makes the gesture feel cumbersome compared with instant full‑screen switching, yet it remains a vivid illustration of the Amiga’s ability to treat screens as independent, movable layers. The article notes that many advanced topics—such as the blitter, sprites, and planar‑graphics tricks—are only touched on, pointing readers to further sources for deeper exploration.